Comments

Thanks for drawing my attention to the fact that the Bowman does not leap. I will correct my piece article Man and Beast 21: Lords High Everything-Else to take this into account when I have more time. I would still hold that Equiadvancer is the logical generic term for a piece that goes exactly halfway to the piece that it captures.

If the Bowman moved as a Knight but captured normally, it could be thought of as a Knight equivalent of the Advancer. However, it is actually a complex Moo that captures as an Advancing Knight on the matching path.
The Bowman can also be thought of as capturing along a length equal to its movement, instead of just one square like the Advancer. We can extrapolate this to a Rook. Such a piece would move as a non-capturing Rook, but a piece the same amount of squares away in the same direction as the Rook from its starting position would be captured, regardless of intervening pieces. The Bowman-Rook is not as strong as you may think, because the more spaces it moves the more spaces away the piece must be exactly. The Bowman-Rook cannot capture a piece when it moves more than one-half board length, so can only capture if it moves 3 squares or less on a standard board. The Bowman-Rook becomes weaker toward the edges as its attacks are reduced even if they fit on the board sometimes, so it is weaker at long range.